Generally, a circuit breaker is an electric protecting apparatus mounted between an electric source and load units for protection of load units such as a motor and a transformer and an electric line from an abnormal current (a large current caused by i.e., short circuit and ground fault) generated at an electric circuit such as a power transmission/distribution line and private power transforming facilities. In other words, a circuit breaker is an automatic electrical switch that stops or restricts the flow of electric current in a sudden overloaded or otherwise abnormally stressed electrical circuit. A circuit breaker provides automatic current interruption to a monitored circuit when undesired over-current conditions occur. The over-current condition includes, for example, arc faults, overloads, ground faults, and short-circuits.
Furthermore, the circuit breaker may manually open or close the electric line under normal use state, and open or close the line from a remote distance using an electric manipulation unit outside a metal container and automatically break the line during over-current and short-circuit to protect the power facilities and load units.
In order to break the electric line, the air circuit breaker is equipped with a stationary contactor and a movable contactor at a breaking mechanism where a current is made to flow in normal situation by connecting the stationary contactor and the movable contactor, and when there occurs a flaw at any portion of the line to allow flowing a large current, the movable contactor is instantly separated from the stationary contactor to open the circuit, thereby interrupting the flow of the large current.
Meanwhile, a circuit breaker may be classified into an air circuit breaker, a hydraulic circuit breaker and a spring circuit breaker in accordance with manipulation method. In addition, the circuit breaker may be classified into an air circuit breaker (ACB), and a gas circuit breaker (GCB) in accordance with used arc extinguishing medium, and even in this case, a similar effect is achieved.
The circuit breaker is typically mounted with a separate auxiliary contact apparatus, which is a device for transmitting a signal to outside according to opening/closing of a breaker mechanism, i.e., connection and breaking of a movable contactor and a stationary contactor.
Now, an apparatus for auxiliary contact of circuit breaker (hereinafter referred to as auxiliary contact apparatus) is explained in more detail.
When an electric line under a normal use is conducted, an indicator connected to the auxiliary contact device indicates a connected state, in which case a movable contactor is connected to a stationary contactor. However, when there occurs a flaw at any portion of the line to allow flowing a large current caused by, for example, short circuit or ground fault, an open/close mechanism that is driven by a detector signal detecting the abnormal current is activated to rotate an open/close axis, and the movable contactor is instantly separated from the stationary contactor in response to the rotation of the open/close axis to open the circuit, thereby interrupting the flow of the large current. An ON/OFF switch of the auxiliary contact apparatus is turned on and off by a linkage communicating with the open/close axis, and an outside indicator connected to the ON/OFF switch indicates that the circuit breaker is interrupted.
FIG. 1 is a perspective view illustrating an external look of a body of a typical circuit breaker, FIG. 2 is a perspective view illustrating an auxiliary contact apparatus according to an exemplary implementation, FIG. 3 is a lateral view illustrating a released position of the auxiliary contact apparatus of FIG. 2, and FIG. 4 is a lateral view illustrating a compressed position of the auxiliary contact apparatus of FIG. 2.
Although a body of the conventional circuit breaker is not shown in the drawings, the body 10 includes a detector for detecting an accidental current when the accidental current occurs, an open/close mechanism 20 that is driven by a detection signal of the detector, and an open/close axis 30 rotating by being communicated with the open/close mechanism 20, as depicted in FIG. 1.
The body 10 is also mounted therein with a breaker mechanism comprising a stationary contactor and a movable contactor that are mutually connected or interrupted by the rotation of the open/close axis 30 to open or close a conducted electric line. The body 10 further includes an arc distinguishing device distinguishing the arc that is generated on the movable contactor when various internal loads are interrupted.
Particularly, the body 10 is mounted with an external indicator indicating connection and interruption states of the conducted line in response to the rotation of the open/close axis 30, i.e., an auxiliary contact apparatus 40 notifying the connection and interruption states via a lamp or a buzzer.
Referring to FIG. 2, the conventional auxiliary contact apparatus 40 includes a push bar 52 that operates horizontally and vertically by being connected to the open/close axis 30, a drive rotation link 54 rotated by the push bar 52 about a driving shaft 56, and a linkage 50 of a driven rotation link 58 extensively formed from the driving shaft 56 toward a radial direction. An ON/OFF switch 42 of the auxiliary contact apparatus 40 is compressed or released by the activation of the driven rotation link 58 for on and off operation, whereby connection or interruption of the circuit breaker is indicated on the outside indicator.
Referring to FIG. 3, when the convention line is conducted, the stationary contactor and the movable contactor inside the body 10 are connected to cause the open/close axis 30 to rotate clockwise. As a result, the push bar 52 connected to the open/close axis 30 does not push the drooped drive rotation link 54, where the driven rotation link 58 does not compress the ON/OFF switch 42 and is in the state of being released without the rotation of the driving shaft 56. The external indicator connected to ON/OFF switch 42 indicates that the circuit breaker is in the connected state.
However, as shown in FIG. 4, if the accidental current is detected to cause the circuit breaker to be in the interrupted state, the movable contactor is separated from the stationary contactor to allow the open/close axis 30 to rotate counter-clockwise. Resultantly, the push bar 52 connected to the open/close axis 30 is pushed upward to allow the drive rotation link 54 to push the push bar 52. Successively, the driving shaft 56 is rotated along by the rotation of the drive rotation link 54 to rotate the driven rotation link 58 counter-clockwise. In doing so, the rotation of the driven rotation link 58 compresses the ON/OFF switch 42 to allow the external indicator connected to the ON/OFF switch 42 to indicate that the circuit breaker is interrupted.
Meanwhile, a strong impact is generated by the operation of the open/close mechanism 20 during interrupting operation of the breaker mechanism, whereby the open/close axis 30 is excessively rotated, the rotational power of which is transmitted to each link. Furthermore, the rotational force transmitted to the driven rotation link 58 is strongly transmitted to the ON/OFF switch 42 as an impact force. The excessive rotation of the open/close axis 30 brings about an over-stroke of the push bar 52 to cause the linkage 50 rotate beyond an established rotational radius. In the end, the impact caused by the over-stroke is transmitted intact to the ON/OFF switch 42 that is compressed or released by the driven rotation link 58.
As noted from the foregoing, there are problems in the conventional auxiliary contact apparatus in the circuit breaker in that the ON/OFF switch may be damaged or destructed by the over-stroke from the operation of the linkage communicating with the open/close axis. This inevitably leads to an erroneous operation and degraded reliability of the auxiliary contact apparatus caused by the repeated on-off operation thereof.